Python

Conditionnals

x = 1
if x == 2:
   a = 3
else:
   a = 2
a

One-line ternary condition

In languages with a C-syntax, it is possible to write an conditional ternary expression: a = (x == 2) ? 3 : 2. It Python, we can do the same with a more understandable syntax:

a = 3 if x == 2 else 2
a

Easy-to-read conditions

In Python, conditions can be written for normal people.

age = 5
print("young" if 0 < age < 18 else "old")

invitationList = ["Alan", "Bob", "Christine", "Dylan", "Emeline", "Franck"]
me = "John"
if me not in invitationList:
    print("you cannot enter")

Assignments in conditions

According to https://peps.python.org/pep-0572/, it is possible to make an assignment in a condition, like in C. To do that, we use the Walrus operator :=.

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
if (n := len(a) > 10):
    print(f"List is too long ({n} elements, expected <= 10)")

No switch, sorry

There is no switch in Python, contrary to C. See https://peps.python.org/pep-3103/

Pattern matching

Here is an example of pattern matching (available in Python 3.10, https://docs.python.org/3/reference/compound_stmts.html#match).

i=0
match i:
    case 0: print("zero")
    case _: print("non zero")

While loops

x = 0
while x < 10:
    x += 1

For loops

In Python, it is possible to write for loops. They take the form of for i in BLOUP where BLOUP is an iterable. It matches somehow the theory of primitive recursive functions: we know that for loops terminates if the iterable object produces a finite number of elements.

for i in range(10):
    print(i)

Generators

A generator is a special kind of function that contains the keyword yield. It returns an iterable object.

def squares(start, stop):
    for i in range(start, stop):
        yield i * i

for i in squares(1, 6):
    print(i)

1
4
9
16
25

Comparing C and Python

import this

The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

History

• PEP 7 – Style Guide for C Code
• PEP 8 – Style Guide for Python Code
• PEP 20 – The Zen of Python
• PEP 257 – Docstring Conventions